Antenna system



7 Sept. 28, 1937. c. FQRBES 2, 8

ANTENNA SYSTEM Filed Aug. 4, 1934 2 Sheets-Sheet 1 INVENTOR HENRY C.FORBES Mp 5, M14

ATTORNEY Sept. 28; 1937. H. c. FORQBES 2,094,168

ANTENNA SYSTEM Filed Aug. 4, 1934 2 Sheets-Sheet 2 INVENTOR hgE NRY c.amass.

ATTOR EY Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE,

ANTENNA SYSTEM poration of Delaware Application August 4,

3 Claims.

This invention pertains to radio antenna installation and particularlyto antenna installations that are adapted to be used for automotivevehicles.

One of the objects is to provide an antenna installation that willreduce power wire and trolley wire pick-up by a radio antenna, withoutproportionately reducing the signal pick-up.

Another object is to provide an antenna installation in balancedrelation to ground, such as the car frame.

These objects are accomplished by variously installing on a vehicleantenna parts of proper characteristics, and connecting them in seriesand with a transmission system to the receiver.

A further object, is to provide a unitary struc ture for thetransmission system in the form of a harness for coupling the antenna toa receiver, so that the signal pick-up may be impressed upon thereceiver without an attendant impression of power wire and trolley wirepick-up, or ignition noises.

These and other objects are accomplished by providing a coupling unitfor the antenna and receiver that includes a pair of matchingtransformers each having a coil connected by leads with a coil of theother, and the transformers, and lead wires incased in a shieldingbraid, or the like, adapted for grounding to the frame of the vehicle.

One of the objects is to provide an antenna system that increases theratio of signal strength to noise.

This is accomplished by providing an antenna that takes advantage of thedifference in directions of the approaching wave fronts that generallyexists between the signal and noise w'aves.

Another object is to provide an antenna system that increases the ratioof signal strength to noise and efficiently transmits the signal to aradio receiver.

This is accomplished by providing an antenna that takes advantage of thedifference in directions of approaching wave fronts that generallyexists between the signal and noise waves, and by providing a propertransmission systemfor impressing the signal thus isolated upon thereceiving circuit.

Further objects and advantages of the present invention will beapparent'from the following description, reference being had to theaccompanyingdrawings wherein a preferred embodiment of the presentinvention is clearly shown.

In the drawings:

Fig. 1 is a perspective View ofa vehicle illus- 1934, Serial No. 738,447

trating in diagrammatic form the instant invention as applied thereto.

Figs. 2, 3, and 4 each illustrate modifications of the installation.

Fig. 5 is a longitudinal sectional view, with certain parts broken away,illustrating structural details of a harness unit or transmission lineforming part of the instant invention.

Fig. 6 is a transverse sectional view, substantially as indicated by theline and arrows 66 of Fig. 5, and

Fig. '7 is a transverse sectional view substantially as illustrated bythe line and arrows 1-1' of Fig. 5.

One of the chief objections to automotive radio in a city is the largeamount of noise pick-up with a sensitive receiver when driving under atrolley wire, power line, or in fact, any wires carrying electriccurrent, having switching transients or commutation disturbances.

A like objection is found in radio installations in dwellings and thelike where the receiver is located in close proximity to power wires orconductors. While the instant invention ofiers a solution for all suchproblems, it will be described principally as an installation forvehicles, but it is to be understood that the disclosure pertains to andproposes to include an installation on'immovable structures where likeproblems are to be solved.

It is well known that radio waves are polarized, that is, have acomponent largelyin a single plane. In the broadcast band, the waves arelargely plane polarized, and are substantially vertically polarized,particularly in the vicinity of the broadcast station. At greaterdistances, the wave front may be inclined to the vertical, but thepolarization remains largely plane, and largely vertical.

The common sources of noise disturbances are,

however, such that the field components often exist in other planes,particularly when the source is a nearby trolley wire or power wire.This difference in the plane of polarization of the noise disturbancesand the desired signals makes possible the use of a type of antenna foran automobile that will permit the desired signal pick-up, but whichwill not pick up the noise disturbances, so that an improvement in thesignal to noise ratio, over the usual car antenna will be possible.

This may be illustrated by assuming that a vehicle equipped with theproposed antenna installation is situated somewhat remote from thebroadcast station, and moving along a street with an overhead trollywire. It is well known that energized conductors, which include both thetransmitting antenna and the trolly wire, are attended by radiationfields, which are the carrier, so to speak, of the signal and noiseimpulses. Energized conductors are also attended by induction fieldsthat are relatively strong in the near proximity of the conductors butrapidly diminish at increasing distances from the conductor. Theprinciple of operation that is believed to obtain comprehends therelation of the radiation and induction fields of both the power wireand the transmitting antenna.

These various fields are conceivable as each comprising more or lessconcentric waves emanating in substantially perpendicular planes fromthe respective conductors. As is well known to those skilled in the art,at the above assumed position of the vehicle, the induction field of thepower wire is much the stronger, since that line being of low frequencyis attended with only a negligible radiation field. The transmittingantenna being at a relatively great distance, and of high frequency, ismanifest at the assumed location of the vehicle, by the radiation fieldonly; the induction field having diminished so much as to be negligible.Therefore, the receiving antenna of the vehicle in the assumed location,will be subjected only to the induction field of the power wire and theradiation field of the transmitting antenna. The wave fronts of theradiation field from the transmitting antenna, due to the greaterdistance, and therefore large radius of curvature, are substantiallyvertical by the time they reach the receiving antenna, and create apotential in the receiving antenna that is greater than the groundpotential, so that a signal voltage is applied to the receiver from theantenna. The wave front of the induction field from the trolly wire, thenoise source, due to the lesser distance, and relative position of thereceiving antenna system, will be practically parallel to the earthsurface, and it creates two and opposite currents in the antennasections that cancel out in the winding of the transformer. Thus thesignal from the broadcast station will be effectively picked up withoutthe attendant noise component.

As a practical solution of this problem, a plane or position is foundfor an antenna on an auto mobile, that will permit efficient signalpick-up and yet will have little or no pick-up for noises from nearbypower lines. Such a desirable location for an antenna on an automobile,and one answering the requirements is in the top, where antenna partssuch as a piece or pieces of screen, approximately the equivalent of 3feet x 5 feet or an equivalent area may be used as suggested in thedrawings. But other types and forms of antenna-elements may be used asan alternative, as will appear from the pages that follow. A leadin isbrought down one of the posts to the receiver and in order to preventspark noise pick-up by the lead-in, it is shielded, at least for a partof its length. If the lead-in is shielded, then it may be run close toother conduits or tubing, and yet be effectively shielded fromdisturbing noises. The capacity of the antenna itself is comparativelylow, certainly less than 200 micro-micro-farads, and probably less than125 micro-micro-farads, and this resulting mis-match of impedances, whensuch a low capacity antenna is connected to a high capacity lead-in,would effect considerable losses in efficiency.

It is proposed therefore to provide a coupling means at the junction ofthe antenna and leadin, so as to properly match the impedance of ashielded lead-in to the antenna, thus permitting the use of a totallyshielded lead-in, which to gether will give improved antenna efiiciency,due to proper matching. A coupling device at the receiver, is sodesigned as to match the input impedance of the receiver to that of theline. This may be accomplished by a device separate from the regularantenna coil, if necessary, and where so done both coupling devices maybe enclosed within the shield as a unit of construction andinstallation.

With particular reference to the drawings, Fig. 1 illustrates indiagrammatic form an installation of radio receiver and antenna, with atransmission line therefor, and depicting all of the features of theinstant invention. In this particular instance, the plane desirable fordisposition of the antenna exists in the top or roof 2% of a vehiclegenerally indicated by reference numeral 22. Two antenna parts 24 and26, which may be embodied in appropriate sections of copper screening,are embodied in the top or roof construction, and are serially connectedto a winding 28 of a coupling unit or impedance matching device 29.Inductively coupled with the winding 28, there is a second winding 33whose terminals are joined to a pair of leads or conductors 32 and 34.The conductors are of sufiicient length to make a convenient mounting ofa radio receiver 36, in some available space about the vehicle body,which is diagrammatically illustrated in the drawings as back of themotor-board and in front of the instrument panel, or that space usuallyrecognized as the cowl of an automobile.

While the leads 32 and 3 1 are illustrated as being twisted it is notnecessary that they be twisted but they may be parallel if closelyspaced. A second coupling unit or impedance matching device 48, has awinding 62 whose terminals are also connected with the conductors 32 and34, and the winding 42 is inductively coupled to a second winding 44whose leads 43 and 45 are adapted for connection into the hereinbeforementioned receiver 36.

That part of the transmission line between the antenna parts and thereceiver has been previously designated as a harness, and it isconstructed as a subassembly unit according to the disclosure set out inFigs. 5, 6 and 7. In addition to the elements just set out, the harnessincludes shielding means 45 which substantially encloses both of thecoupling units 29, 49, as well as the conductors or leads joining thewindings of one with the windings of the other.

As disclosed in Fig. 1, the antenna parts 24 and 2B, are mounted onopposite sides and similarly placed as respects the medial line of thevehicle, In Fig. 2 the installation is varied somewhat, in that theantenna parts 2G and 26 are arranged in a fore and aft position andsubstantially similarly located along the medial line of the vehicle.With respect to Fig. 3, the antenna parts comprise loops and branches ofa more or less continuous conducting element as indicated at 24a, 24b,24c and 26a, 26b and 260. According to the disclosure in Fig. 4, theantenna elements comprise metal bands 24d and 26d forming the tirecovers in the popularly known sport model vehicle. In each instance ofthe disclosures of Figs. 1 to 4, inclusive, the antenna parts areconnected in series through the coupler winding 28 included in thetransmission line which eventually leads to the receiver 36. In eachinstance the shielding means at some point adjacent the ends thereof, ornear the couplers 29 and 40 is provided with grounding connections tothe frame of the vehicle as generally indicated at 48 and 50. Theantenna parts of course are provided with properly insulated supports.

For details of construction of the harness,reference is now made toFigs. 5, 6 and 7, which disclose the coupler units 29 and 40 as mereenlargements situated at each end of the transmission line. Inasmuch asthe construction of both the coupler units may be substantiallyidentical, a detail illustration has been made of but one, and it may beassumed that the internal construction of the unit 40 answers thedetails illustrated in Fig. 5, as regards the construction of the unit30. One detailed form of construction, is that in which a nonconductingor insulating tube 52 is provided, and within which is mounted thewinding 28 of the coupling unit. The tube 52 also provides adequatesupport for the second winding 30 of the unit and from which the endturns may be united with the leads 32 and 34 and extended substantiallyalong the axis of the tube toward the other coupler unit, whereconnection may be made with the winding 42 thereof. In this instance,which illustrates a convenient and a desirable construction, the winding28 has its end turns terminating in the leads or conductors 56 and 58,but are adapted to connect with the antenna parts as designated thereonby the legend.

The shielding 46, comprises a plurality of metallic strands 60 that arebraided into substantially tubular form, to provide a metallic sheathextending throughout the length of the conductors 32 and 34, and extendover the coupler units 29 and 40 where the ends of the braided strandsmay be compressed about the leads joining the antenna parts and/or thereceiver with the respective coupling units 29 and 40. A convenientmeans for compressing the sheath about the leads resides in the metalband or ring 62 which incidentally may provide the leads 48 or 50through which the grounding connection is made, the ring being bonded tothe metallic strands by solder or the like. Overlying the metallicshield, there is a sheath 64 of insulating fabric which may be braided,woven or otherwise secured, and which may be tinted or colored so as toblend in with the upholstery or interior finish of the vehicle.

A wiring harness constructed in accordance with the disclosuresatisfactorily embodies the improvements set out, and provides aconstruction that is readily adaptable for installation in a vehiclethat is in service, and makes such an installation possible withoutdisfiguring the interior of the vehicle finish, and withoutdisorganizing the general appearance thereof. When the antenna andtransmission line are so installed, the receiving instrument is thenadapted to pick up and sort out signal waves, and efficiently transmitthem to the radio receiver even though the vehicle or other constructionembodying the installation may be in the very near vicinity of a highpowered transmission line, trolley wire or the like. In installations ofthe character disclosed the antenna parts being situated in spacedrelation and in a plane substantially perpendicular to the noise wavefront, apparently cancels out noise impulses received from thedisturbing source Whether or not there is any cancellation of the noiseimpulses, the unit effectively impresses the signal wave receivedthrough the radiation field upon the transmission line in such mannerthat there will be an improvement in the ratio of signal to noise, andthe ultimate result is one in which the signal wave is impressed uponthe receiver unimpaired by the noise component.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. In a radio installation having antenna parts remotely situated withrespect to a receiver, a harness adapted for coupling the antenna partsto the receiver, comprising in combination, a pair of insulating tubes,transformer windings disposed within each tube, the windings of one tubehaving conductors adapted for connecting with the antenna parts, and thewindings of the other tube having conductors adapted for connecting tothe receiver, other transformer windings disposed about the tubes andinductively coupled with the inner windings, a pair of leads joining theouter windings of one tube with the outer windings of the other tube, afabricated sheath of metallic strands overlying the leads and thetransformer windings, and means compressing the fabricated sheath aboutthe conductors between the winding and the antenna parts and receiverrespectively.

2. In a radio installation having antenna parts remotely situated withrespect to a receiver, a harness adapted for coupling the antenna partsto the receiver, comprising in combination, a pair of insulating tubes,a Winding supported within each tube and having a pair of short leadsfor connecting a winding each with the antenna parts and the receiver, asecond winding secured outside of each tube, a pair of conductorsextending between and connecting the second windings into a closedconductive path, a shield element of woven metallic strands extendingthroughout the conductors and beyond each tube and its supportedwindings, a metallic ring compressing the ends of the metallic strandsabout the leads of each inner winding and a jacket of insulatingmaterial substantially covering the shield element.

3. An antenna installation, comprising in combination, antenna meanscomprising parts of l which lie in a plane substantially parallel to thewave front of the noise field, and substantially perpendicular to theWave front of the signal field, means connecting the antenna parts inseries and including a transformer winding, a second transformer windinginductively coupled to that first mentioned, and a transmission lineextending between the second winding and the receiver, said transformerwindings and transmission line operating to impress the signal Wavereceived upon the receiver unimpaired by the noise component.

HENRY C. FORBES.

